Feat/adding Discord icon

[omurilo]

Is your feature request related to a problem? Please describe.

Yes, today I had the need to add the discord icon to my project but it didn't exist on nes.css. Discord is the most popular platform to gamers and developers community, why NES.css haven't that icon?

Describe the solution you'd like

I don't want a solution, i have a solution.

Describe alternatives you've considered

I've considered make a solution, so i made and learned a lot from it.

Additional context